Modern high performance automobiles, such as those used in automobile racing, incorporate dry sump oil pump systems to provide engine lubrication under the extreme operating conditions encountered in automobile racing. In dry sump systems, oil is stored in a separate oil tank or sump that, unlike the wet sump system of conventional passenger automobiles, is separate from the engine. The oil pump and associated oil lines circulates oil from that sump to the engine. After use in the engine, the oil is pumped out of the engine by scavenger pumps acting through oil pick-ups appropriately placed on the engine's underside, the engine oil pan, and is returned to the sump for recirculation. The oil is recirculated in that way through the engine in a continuous process. In practice the scavenger pumps are integrally packaged with the principal oil pump and are driven by the same pulley and shaft system that drives the principal oil pump.
A typical scavenger pump system may contain one, two, three or more scavenger pumps, depending upon one's performance needs, whose outputs are placed in common in the pump unit so that the oil may be returned to the sump by a single return oil line. Each scavenger pump employs a pair of rotors on separate shafts arranged for counter rotational movement within a compartment with the compartment open to the salvage oil line. Rapid intermeshing rotation of the engaged rotors creates a low pressure or suction that sucks the salvageable oil through the intake and then forces that oil out the drain end to the sump's oil return lines. Hence, the greater the number of salvage pumps employed, the greater vacuum or sucking is achieved. A particular form of rotor, referred to as the Roots rotor, long ago found wide acceptance in scavenger pumps for such application.
The oil pump system is not sealed to the environment and, consequently, air enters the automobile's oil system. In addition to oil, thus, the oil sump also contains air. Air is also mixed within the oil. Indeed the more effective the scavenger pumps and oil pumps, it is found, the greater percentage of air is found mixed in the oil. Since air does not lubricate engine parts nor provide cooling of those parts as effectively as oil, unless the air is removed, one finds that, although the requisite volume of oil is seemingly being pumped to provide sufficient cooling and lubrication to the engine, in fact, the lubrication and cooling is insufficient. As a consequence the engine may overheat and bearings and other parts may prematurely fail.
The foregoing difficulty was earlier recognized by the Cosworth company of the United Kingdom. That company introduced an air-oil separator for attachment onto an oil pump assembly. The Cosworth separator separated the oil from the air and separately returned those ingredients to the oil sump, the air to the top side of the pump and the oil to the lower portion containing the oil.
Briefly, the Cosworth air oil separator incorporates a rotating drum and an impeller, containing outwardly extending vanes, positioned within the drum and means to rotate the drum and impeller in opposite rotational direction. Through centrifugal force scavenged oil introduced into the separator is thrown outwardly to the drum. In turn, holes through the drum allows the oil to exit an area on the outside the drum. Air, which becomes concentrated in the central region by the impeller, exits through passages formed in the impeller. The unit also incorporated a shuttle valve that blocked the oil outlet, when no oil was present in the separator, so that air is not forced into the return oil line. Although successful in result, the complexity of the drum impeller arrangement only briefly discussed, translates to a very high cost for the unit in practice, and, hence, as a practical matter, limited availability of that separator to the large number of automobile hobbyists and professionals involved in automobile racing.
An object of the present invention, thus, is to provide an improved oil pump system and, particularly, an air-oil separator of simpler construction than heretofore and consequent reduced manufacturing costs.
A further object of the invention is to provide an air oil separator that easily integrates within a dry sump type oil pump assembly to form overall a compact physical assembly that is easily handled and installed within an automobile.
And an additional object of the invention is to provide an air oil separator that avoids use of the complex counter rotating drum and impeller system for air oil separation.